Improved Measurement of CP Violation in Neutral B Decays to c cbar s

TL;DR

This paper reports updated measurements of CP violation parameters in neutral B meson decays to charmonium states, using a large data sample from the BABAR experiment, providing more precise values of sin2beta and |lambda|.

Contribution

It provides the most precise measurements to date of CP asymmetries in B decays to charmonium, refining our understanding of CP violation in the Standard Model.

Findings

sin2beta = 0.714 +/- 0.032 (stat) +/- 0.018 (syst)

|lambda| = 0.952 +/- 0.022 (stat) +/- 0.017 (syst)

Results are consistent with Standard Model predictions.

Abstract

We present updated measurements of time-dependent CP asymmetries in fully-reconstructed neutral B decays to several CP eigenstates containing a charmonium meson. The measurements use a data sample of (383 +/- 4) x 10^6 Y(4S)-> BBbar decays collected with the BABAR detector at the PEP-II B factory. We determine sin2beta = 0.714 +/- 0.032 (stat) +/- 0.018 (syst) and |lambda| = 0.952 +/- 0.022 (stat) +/- 0.017 (syst).